let a:number = 123
let b:number|string = 'helo'

//b = a

//error
//a = b

let c:{username:string} = {username:'123'}
let d:{username:string;age:number} = {username:'123',age:123}
//error
//d = c;

c = d

function foo1(n:{username:string}){}
foo1({username:'123'})

//error
//foo1({username:'123' , age:123})
let z = {username:'123' , age:123}
foo1(z);

